In a network communication environment, such as the Internet, a client computing device (client) may utilize a software browser application to initiate network connections with server computing devices (servers), and subsequently request content from those servers. Servers may respond to client requests for content, but in typical Hypertext Transfer Protocol (HTTP) based communications, servers do not initiate transfers of content to clients. A request from the client is typically required in order to initiate any transfer of data from the server to the client. Other protocols, such as SPDY, enable a server to initiate a data transfer to a client over a connection initiated by the client device.
Servers may provide indications to clients regarding which network resources to retrieve to improve the performance of future content requests and processing. Such predicted or anticipatory retrieval, also known as prefetching, may be implemented through use of a prefetch hint embedded within a Hypertext Markup Language (HTML) file. In a typical implementation, servers can determine which content a client is likely to request next, and include a prefetch hint identifying which linked content to proactively fetch. Clients receiving an HTML file with a prefetch hint may request the indicated content before it is requested by a user.